Environmental Impact Of Concrete Research Articles

Environmental impact of concrete containing high volume fly ash and ground granulated blast furnace slag

Concrete production is energy-intensive and has an adverse impact on the environment due to the raw materials involved. Currently, India has abundant reserves of fly ash and ground granulated blast furnace slag (GGBS). Despite various applications, fly ash often ends up in landfills. Given its abundance, there is a growing interest in utilising substantial quantities of fly ash in concrete production. In the current study, M30-grade concrete is designed with very high levels of fly ash and GGBS. Additionally, quick lime (QL) is incorporated as a supplementary agent to augment lime content. A total of twenty concrete mixes have been developed with different combinations of fly ash, GGBS, and QL. Results illustrate that the addition of QL does not show overall strength improvement to the GGBS-based mixes, but it impacts on fly ash-based mixes. The targeted design strength is achieved with 70% cement replacement with fly ash and QL. The strength development depends on the pozzolanic reaction initiated and the formation of hydration products in the system. The environmental impact of concrete is assessed by analysing its life cycle assessment using a cradle-to-gate approach. The energy requirement and kg-CO2 eq. emissions depend on the level of cement replacement. The fly ash-based concrete emits less kg-CO2 eq. and requires less energy than the GGBS-based mixes. Overall, the designed strength is achieved with 65% fly ash, requiring 59% less energy, reducing 54% CO2 footprint, 56% GWP100, 80% HTPinf, 46% ODPinf, and cost by 34% compared to OPC-based concrete.

On the Performance Analysis and Environmental Impact of Concrete with Coal Fly Ash and Bottom Ash

Coal is a commonly used fuel by coal power plants that produce coal fly ash and coal bottom ash (coal FABA) as byproducts. The latest regulation in Indonesia changes coal FABA classification to non-toxic waste, which opens up its utilization possibility. This paper analyses the coal FABA potential from Suralaya Coal Power Plant as concrete material and its environmental impact. To determine coal FABA potential, the methods used in this paper are slump test, compressive strength test, flexural strength test, and carbon footprint calculation. This paper shows that concrete mixture with coal FABA content has a lower slump value, lower compressive strength, and generally lower flexural strength. Furthermore, the carbon footprint calculation result shows that concrete mixture with coal FABA content has lower CO2 emissions than conventional concrete. Finally, the result shows that concrete with coal FABA could be used as non-structural concrete.

Environmental Impacts of Concrete in Chemical Parameters of Soil

Cement is a major construction material used in civil engineering works due to which its demand is very high. Increase in concrete use has both advantages and disadvantages. Cement materials used is directly or indirectly related to raw material use, energy consumption, air emissions, water pollution, solid waste, health concerns etc. To study direct environmental impact of cement use, soil samples of mass concreted area were collected and change in selected soil parameters were examined from laboratory experiments. Total nitrogen, available phosphorus, available potassium, pH, organic matter, soil texture and moisture content of soil samples were obtained from the lab. Each soil parameters were compared with acceptable range for normal soil.

Influence of cement strength class on environmental impact of concrete

Traditional approaches to reducing the CO2 emissions of cement production are effective yet insufficient, which has driven new research and innovations. A potential alternative that has been poorly explored is optimizing the physical and chemical characteristics of cement to enhance the dosage efficiency for concrete, which can reduce both cement consumption and CO2 emissions. This approach demands an understanding of the potential savings according to the cement strength. In practical terms, increasing the cement strength requires more electric energy to grind cement into finer particles, which ensures that most of the clinker and other reactive particles are hydrated at 28 days; and increasing the reactive phases of the cement, such as the clinker content. Both options improve cement reactivity and can reduce cement consumption to achieve the same mechanical performance of concrete. The objective of this study was to investigate the potential reduction in the CO2 footprint of concrete mixes with cements of different strength classes and discrete clinker substitution ratios. The effect of grinding finer cement on reactivity was also evaluated. The carbon abatement costs were estimated according to the additional CO2 emissions from cement grinding and potential CO2 reduction from a smaller dosage.

Environmental Impact of Concrete and Concrete-Based Construction Waste Leachates

Studies concerning environmental impact of construction materials are very rarely based on experiments performed with real mixed samples and test organisms (ecotoxicological bioassays). In our study, ecotoxicity of two concrete samples from different producers and one concrete-based construction waste in leachate form were assessed. Leachates were treated by various designs, i.e. i) without any treatment, ii) original pH + nutrients addition, iii) pH adjustment to 7.0, and iv) pH adjustment to 7.0 + addition of inorganic nutrients. Ecotoxicological bioassays with freshwater algae Desmodesmus subspicatus, freshwater plant Lemna minor and freshwater invertebrate Daphnia magna were performed. The metal content was determined both in solid samples and leachates. Results showed differences in toxicity level among the concrete sources when original leachates without any treatment were tested. On the contrary, the test design recommended by Czech legislation, i.e. lowering of the pH and addition of nutrients usually significantly decreased the sample toxicity and the potential differences among concrete samples. We suggest that the toxicity of concrete leachates may result not only from the highly alkaline pH but also from the potential persistence of high pH values both within dilution process and time. The higher toxicity was in accordance with higher level of leachate conductivity. Therefore, for the purposes of aquatic ecotoxicity assessment, we recommend either making no pH adjustment or performing the bioassays both with treated and untreated leachates.

A comprehensive investigation into the effect of temperature variation on the mechanical properties of sustainable concrete

Minimizing the production energy and resources consumption are the key principle for engineering sustainability. In the case of concrete structures, this concept can be achieved by the use of materials in the most efficient way considering in the mix design the optimal mechanical and durability properties. The substitution of ordinary Portland cement for other supplementary cementitious materials is assessing the possibility of enhancing the sustainability and decreasing the environmental impact of concrete. Mass concrete is rich in cementitious materials which results in high temperature within the concrete, hence several hazards such as cracking or temperature differences between the interior and the surface of concrete could be prevented. An experimental study evaluated on several one cubic meter sized concrete elements in which during the primary phase of hydration, the temperature variation is recorded in several location offsets with respect to time. Thermal variations results are analyzed in accordance with the cement type, CO 2 emission production of cement, compressive strength, water tightness, drying shrinkage and rapid chloride migration coefficient. The results indicate that slag cement CEM III/B 32.5, that incorporates highest amount of slag, ensured improved mechanical, thermal and durability properties in comparison with ordinary Portland cement CEM I 32.5.

Photovoltaic's silica-rich waste sludge as supplementary cementitious material (SCM)

Waste sludge, a solid recovered from wastewater of photovoltaic-industries, composes of agglomerates of nano-particles like SiO2 and CaCO3. This sludge deflocculates in aqueous solutions into nano-particles smaller than 1μm. Thus, this sludge constitutes a potentially hazardous waste when it is improperly disposed. Due to its high content of amorphous SiO2, this sludge has a potential use as supplementary cementitious material (SCM) in concrete. In this study the main properties of three different samples of photovoltaic's silica-rich waste sludge (nSS) were physically and chemically characterized. The characterization techniques included: scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), nitrogen physical adsorption isotherm (BET method), density by Helium pycnometry, particle size distribution determined by laser light scattering (LLS) and zeta-potential measurements by dynamic light scattering (DLS). In addition, a dispersability study was performed to design stable slurries to be used as liquid additives for the concrete production on site. The effects on the hydration kinetics of cement pastes by the incorporation of nSS in the designed slurries were determined using an isothermal calorimeter. A compressive strength test of standard mortars with 7% of cement replacement was performed to determine the pozzolanic activity of the waste nano-silica sludge. Finally, the hardened system was fully characterized to determine the phase composition. The results demonstrate that the nSS can be utilized as SCM to replace portion of cement in mortars, thereby decreasing the CO2 footprint and the environmental impact of concrete.

Environmental assessment of green concrete containing natural zeolite on the global warming index in marine environments

The main air pollutant in the concrete industry is cement responsible for approximately 6% of man-made CO2 emissions. Due to growing concerns for global warming, reducing the consumption of traditional Portland cement and improving mechanical properties of concrete composites have become two important sustainable development issues in recent decades. Zeolite, a type of natural pozzolanic material, has been used as an alternative to improve the durability of concrete. In this study, environmental impact of concrete containing zeolite and conventional one on the global warming potential are assessed by applying life-cycle assessment method. The calculations indicated that replacing 10%, 20% and 30% of cement with zeolite amounted to a 60.3%, 69.7% and 64.3% global warming potential reduction, respectively, which proves the effectiveness of zeolite in making highly environmentally friendly concrete.

Properties and mechanical–environmental efficiency of concrete combining recycled rubber with waste materials

This paper investigated the effect of combining rubber crumbs with recycled aggregates and fly ash on the mechanical properties and environmental impact of concrete. Increasing the amount of rubber crumbs linearly reduced strength and Young's modulus regardless of aggregate or binder type, but the effect of recycled aggregate on strength decreased as the amount of rubber crumbs increased. Air permeability also increased with the amount of rubber crumbs but the effect of recycled aggregates varied, as it was constant in the case of non-fly ash but completely reduced with fly ash. The mechanical–environmental efficiency was calculated by weighting the strength by the volume of raw materials, and recycled aggregates were found to have the highest efficiency whereas rubber crumbs were inefficient. When setting a specific strength level, the weighted strength could be used to select the most efficient combination of waste materials.

コンクリートの環境負荷評価研究小委員会報告

コンクリートの環境負荷評価手法の概念, 計算方法および運用に関する動向について調査研究を行い, これらを基に, 簡便な相対評価手法としての環境ポイントを提案するとともに, コンクリート構造物の環境負荷評価を実施する一方法について提案を行った。